Miller MT-24 F-25-1 Owner's manual

Brand: Miller

Model: MT-24 F-25-1

Category: Welding System

Type: Owner's manual

This manual is also suitable for

cover 8/92 – SA-145 666-B PRINTED IN USA

Read and follow these instructions and all

safety blocks carefully.

Have only trained and qualified persons

install, operate, or service this unit.

Call your distributor if you do not understand

the directions.

Give this manual to the operator.

For help, call your distributor

or: MILLER ELECTRIC Mfg. Co., P.O. Box

1079, Appleton, WI 54912 414-734-9821

OWNER’S

MANUAL

June 1993 Form: OM-206C

Effective With Serial No. KD375312

CC/DC Welding Power Source

For GTAW And SMAW Welding

120 A At 25 V Or 140 A At 25.6 V, 100% Duty Cycle

152 Model: Single-Phase; 175 Model: Three-Phase Input Power

Thermostat Protection Against Overheating

Touch Start For GTAW Welding

14-Pin Remote Control Receptacle

Maxstar 152 And 175

Miller Electric manufactures a full line

of welders and welding related equipment.

For information on other quality Miller

products, contact your local Miller distributor to receive the latest full

line catalog orindividual catalog sheets. To locate your nearest

distributor or service agency call 1-800-4-A-Miller, or visit us at

www.MillerWelds.com on the web.

Thank you and congratulations on choosing Miller. Now you can get

the job done and get it done right. We know you don’t have time to do

it any other way.

That’s why when Niels Miller first started building arc welders in 1929,

he made sure his products offered long-lasting value and superior

quality. Like you, his customers couldn’t afford anything less. Miller

products had to be more than the best they could be. They had to be the

best you could buy.

Today, the people that build and sell Miller products continue the

tradition. They’re just as committed to providing equipment and service

that meets the high standards of quality and value established in 1929.

This Owner’s Manual is designed to help you get the most out of your

Miller products. Please take time to read the Safety precautions. They

will help you protect yourself against potential hazards on the worksite.

We’ve made installation and operation quick

and easy. With Miller you can count on years

of reliable service with proper maintenance.

And if for some reason the unit needs repair,

there’s a Troubleshooting section that will

help you figure out what the problem is. The

parts list will then help you to decide the

exact part you may need to fix the problem.

Warranty and service information for your

particular model are also provided.

Miller is the first welding

equipment manufacturer in

the U.S.A. to be registered to

the ISO 9001 Quality System

Standard.

Working as hard as you do

– every power source from

Miller is backed by the most

hassle-free warranty in the

business.

From Miller to You

Miller offers a Technical

Manual which provides

more detailed service and

parts information for your

unit. To obtain a Technical

Manual, contact your local

distributor. Your distributor

can also supply you with

Welding Process Manuals

such as SMAW, GTAW,

GMAW, and GMAW-P.

OM-206C – 6/93

EMF INFORMATION

The following is a quotation from the General Conclusions Section of

the U.S. Congress, Office of Technology Assessment, Biological

Effects of Power Frequency Electric & Magnetic Fields –

Background Paper, OTA-BP-E-53 (Washington, DC: U.S.

Government Printing Office, May 1989): “. . . there is now a very large

volume of scientific findings based on experiments at the cellular

level and from studies with animals and people which clearly

establish that low frequency magnetic fields can interact with, and

produce changes in, biological systems. While most of this work is

of very high quality, the results are complex. Current scientific

understanding does not yet allow us to interpret the evidence in a

single coherent framework. Even more frustrating, it does not yet

allow us to draw definite conclusions about questions of possible risk

or to offer clear science-based advice on strategies to minimize or

avoid potential risks.”

To reduce magnetic fields in the workplace, use the following

procedures:

1. Keep cables close together by twisting or taping them.

2. Arrange cables to one side and away from the operator.

3. Do not coil or drape cables around the body.

4. Keep welding power source and cables as far away as practical.

5. Connect work clamp to workpiece as close to the weld as

possible.

About Pacemakers:

The above procedures are among those also normally

recommended for pacemaker wearers. Consult your doctor for

complete information.

Considerations About Welding And The Effects Of Low Frequency Electric And

Magnetic Fields

NOTE

mod10.1 4/93

TABLE OF CONTENTS

SECTION 1 – SAFETY INFORMATION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 2 – SPECIFICATIONS

2-1. Volt-Ampere Curves 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-2. Duty Cycle 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 3 – INSTALLATION

3-1. Typical Process Connections 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-2. Selecting A Location And Moving Welding Power Source 3. . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-3. Selecting And Preparing Weld Output Cables 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-4. Connecting To Weld Output Receptacles 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-5. Remote 14 Receptacle Information And Connections 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-6. Connecting Input Power 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 4 – OPERATION 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 5 – MAINTENANCE & TROUBLESHOOTING

5-1. Routine Maintenance 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-2. Overload Protection 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-3. Measuring Input Capacitor Voltage 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-4. Changing Amperage/Voltage Meter Hold Function 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-5. Troubleshooting 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 6 – ELECTRICAL DIAGRAMS 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 7 – TUNGSTEN ELECTRODE

7-1. Selecting Tungsten Electrode 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2. Preparing Tungsten 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 8 – PARTS LIST

Figure 8-1. Main Assembly 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 8-2. Module, Power & Diode (175 Model Illustrated) 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OM-206 Page 1

SECTION 1 – SAFETY INFORMATION

mod1.1 2/93

Read all safety messages throughout this manual.

Obey all safety messages to avoid injury.

Learn the meaning of WARNING and CAUTION.

1 Safety Alert Symbol

2 Signal Word

WARNING means possible death

or serious injury can happen.

CAUTION means possible minor

injury or equipment damage can

happen.

3 Statement Of Hazard And

Result

4 Safety Instructions To Avoid

Hazard

5 Hazard Symbol (If Available)

6 Safety Banner

Read safety blocks for each sym-

bol shown.

7 NOTE

Special instructions for best oper-

ation – not related to safety.

NOTE

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Disconnect input power before

installing or servicing.

WARNING

READ SAFETY BLOCKS at start of

Section 3-1 before proceeding.

WARNING

CAUTION

MOVING PARTS can injure.

• Keep away from moving parts.

• Keep all panels and covers closed

when operating.

Turn Off switch when using high frequency.

Figure 1-1. Safety Information

SECTION 2 – SPECIFICATIONS

Unless otherwise noted, the 175 model is shown throughout this manual.

NOTE

Table 2-1. Welding Power Source

Specification Description

Type Of Output Constant Current (CC), Direct Current (DC)

Welding Process Gas Tungsten Arc (GTAW), Shielded Metal Arc (SMAW) Welding

Options See Rear Cover

152 Models 175 Models

Rated Weld Output 120 Amperes, 25 Volts DC At 100% Duty Cycle

(See Section 2-2)

140 Amperes, 26.5 Volts DC At 100% Duty Cycle

(See Section 2-2)

Type Of Input Power 230 Volts AC; 50/60 Hz; Single Phase 460 Volts AC; 50/60 Hz; Three-Phase

Input Amperes At Rated Output 25 A 12.5 A

KVA/KW Used At Rated Output 5.85 kVA/3.8 kW 9.56 kVA/5.26 kW

Amperage Range 1-150 A 1-175 A

Max. Open-Circuit Voltage 95 Volts DC 95 Volts DC

Overall Dimensions Length: 16-1/2 in (419 mm); Width: 9-1/2 in (241

mm); Height: 8 in (203 mm)

Length: 16-1/2 in (419 mm); Width: 9-1/2 in (241

mm); Height: 10 in (254 mm)

Weight Net: 31 lb (14 kg); Ship: 36 lb (16 kg) Net: 39 lb (18 kg); Ship: 42 lb (19 kg)

OM-206 Page 2

2-1. Volt-Ampere Curves

ssb1.1 10/91 – SB-151 604 / SB-143 476-B

The volt-ampere curves show the

minimum and maximum voltage

and amperage output capabilities

of the welding power source.

Curves of other settings fall be-

tween the curves shown.

A. 152 Model B. 175 Model

Figure 2-1. Volt-Ampere Curves

2-2. Duty Cycle

CAUTION

EXCEEDING DUTY CYCLE RATINGS will damage unit.

• Do not exceed indicated duty cycles.

warn7.1 2/92

Duty cycle is how long the unit can

operate within a ten minute period

without causing overheating or

damage.

This unit is rated at 100% duty

cycle allowing continuous opera-

tion at rated load.

sb1.1 2/92 – SB-121 591-B / SB-144 507-B

A. 152 Model B. 175 Model

Figure 2-2. Duty Cycle Chart

OM-206 Page 3

SECTION 3 – INSTALLATION

3-1. Typical Process Connections

Welding

Power Source

Work

Welding

GTAW

Power Source

Work

HF Unit

Remote Control

GTAW

Pulse Control

14 Pin

Welding

SMAW

Power Source

Work

Pulsed GTAW

GTAW

14 Pin

Scratch Start

Figure 3-1. Typical Process Connections

3-2. Selecting A Location And Moving Welding Power Source

WARNING

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Disconnect input power conductors from

deenergized supply line BEFORE moving welding

power source.

FIRE OR EXPLOSION can result from

placing unit on, over, or near

combustible surfaces.

• Do not locate unit on, over, or near combustible

surfaces.

• Do not install unit near flammables.

BLOCKED AIRFLOW causes

overheating and possible damage to

unit.

• Do not block or filter airflow.

Warranty is void if any type of filter is used.

FUMES can be hazardous; LACK OF

FRESH AIR AND PROPER

VENTILATION can be harmful.

• Do not breathe welding fumes.

• Place unit only where there is a good fresh air

supply and proper ventilation.

FALLING EQUIPMENT can cause

serious personal injury and equipment

damage.

• Use handle to lift unit.

• Have person of adequate physical strength lift unit.

• Move unit with hand cart or similar device.

swarn11.1* 2/92

Ref. SA-145 666-B

1 10 in (254 mm) Open Space

On Right Side And Rear Of

Unit For Good Airflow

2 Lifting Handle

Use handle to move unit.

3 Rating Label

Locate unit near correct input pow-

er supply.

Right

Rear

Figure 3-2. Location And Movement Of Welding Power Source

OM-206 Page 4

3-3. Selecting And Preparing Weld Output Cables

1 Weld Output Cable

Determine total cable length in

weld circuit and maximum welding

amperes. Use Table 3-1 to select

proper cable size.

Use shortest cables possible.

Do not use damaged cables.

2 Terminal Lug

Use lugs of proper amperage

capacity and hole size for connect-

ing to work clamp or electrode

holder.

3 Insulated Electrode Holder

4 GTAW Torch

Install according to manufacturer’s

instructions.

5 Work Clamp

Install onto work cable.

6 Dinse-Type Connector

Install onto weld cable as shown in

Figure 3-4.

Tools Needed:

10 ft (3 m)

sb6.2* 11/92 – S-0656

Total Cable

Length In Weld

Circuit = 20 ft (6 m)

For Example,

Figure 3-3. Selecting And Preparing Weld Output Cables

Table 3-1. Weld Cable Size*

Total Cable (Copper) Length In Weld Circuit Not Exceeding

100 ft (30 m) Or Less

150 ft

(45 m)

200 ft

(60 m)

250 ft

(70 m)

300 ft

(90 m)

350 ft

(105 m)

400 ft

(120 m)

Welding

Amperes

10 To 60%

Duty Cycle

60 Thru 100%

Duty Cycle

10 Thru 100% Duty Cycle

100 4 4 4 3 2 1 1/0 1/0

150 3 3 2 1 1/0 2/0 3/0 3/0

200 3 2 1 1/0 2/0 3/0 4/0 4/0

250 2 1 1/0 2/0 3/0 4/0 2-2/0 2-2/0

*Weld cable size (AWG) is based on either a 4 volts or less drop or a current density of not more than 300 circular mils per ampere. S-0007-C

1 Weld Output Cable

2 Handle

3 Sleeve

Slide handle onto cable; strip cable

and install sleeve.

4 Connector Body

5 Setscrew

Insert cable with sleeve fully into

connector body, tighten setscrew,

and slide handle over connector.

If job requires cable larger than 3/0

AWG, use 2 ft (610 mm) or shorter

piece of 3/0 AWG cable for Dinse-

Type connector installation. Con-

nect other end of short cable to the

4/0 or larger weld cable.

ST-156 496

Tools Needed:

1 in

(26 mm)

Figure 3-4. Dinse-Type Connector Assembly

OM-206 Page 5

3-4. Connecting To Weld Output Receptacles

WARNING

ELECTRIC SHOCK can kill; ARCING can burn skin or damage electrical equipment.

• Do not touch live electrical parts.

• Turn Off welding power source before making any weld output connections.

• Do not change position of welding cable connectors while welding.

• Be sure connectors are secure in receptacles before welding.

swarn12.2 2/93

1 Positive (+) Weld Output

Receptacle

2 Negative (–) Weld Output

Receptacle

3 Connector

For Electrode Positive (DCEP),

connect work cable connector to

negative (–) receptacle and elec-

trode holder cable connector to

positive (+) receptacle.

For Electrode Negative (DCEN),

reverse cable connections.

Align keyway, insert connector,

and turn clockwise.

4 Remote 14 Receptacle (see

Section 3-5).

Ref. SC-140 373 / Ref. ST-152 126

Figure 3-5. Connecting To Weld Output Receptacles

3-5. Remote 14 Receptacle Information And Connections

sb7.1* 8/92 – Ref. SC-140 373 / Ref. S-0004-A / S-0750

1 Remote 14 Receptacle RC7

2 Keyway

3 Plug

4 Threaded Collar

To connect to this receptacle, align

keyway, insert plug, and tighten

threaded collar.

Socket Information:

Remote Contactor

A +15 volts dc

B Contact closure to pin A completes +15 volts dc con-

tactor control circuit.

Remote Amperage/Voltage Control

C Command reference; +10 volts dc.

D Control circuit common.

E Input command signal (potentiometer wiper or 0 to

+10 volts dc).

K Chassis common.

The remaining sockets are not used.

1 2

Rear Panel

Figure 3-6. Remote 14 Connections

S-0092-F

OM-206 Page 6

3-6. Connecting Input Power

WARNING

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Turn Off welding power source, and disconnect input power before inspecting or installing.

• Have only qualified persons install unit.

• Installation must meet National Electrical Code and all other codes.

swarn3.1 2/93

A. Connecting Input Power To 152 Models

1 230 VAC Cord/Plug

2 230 VAC Grounded

Receptacle

An individual branch circuit capa-

ble of carrying 25 amperes, and

including overcurrent protection

such as fuses or circuit breaker is

required. Recommended standard

fuse or circuit breaker rating is 40

amperes.

Connect input power plug to proper

230 VAC receptacle.

ST-156 250

Figure 3-7. Input Power Connections

B. Connecting Input Power To 175 Models

Table 3-2. Electrical Service Requirements For 175 Ampere Models*

Input Voltage

460

Input Amperes At Rated Output

Recommended Standard Fuse Or Circuit Breaker Rating In Amperes

Input Conductor Size In AWG/Kcmil

Max Input Conductor Length In Feet (Meters)

326 (99)

Grounding Conductor Size In AWG/Kcmil

These values are calculated from the 1990 edition of the National Electrical Code (NEC).

1 Recommended fuse or circuit breaker size is that closest to 150% of rated input amperage of the welding power

source. Article 630-12(a) of NEC allows fuse or circuit breaker sizing up to 200% of rated input amperage.

2 Input conductor size is for insulated copper wire with 75

°C rating with not more than three single current-carrying

conductors in a cable or raceway (Table 310-16 of NEC).

3 Maximum length is to prevent more than a 3% voltage drop between service entrance and input terminals of the

welding power source (Articles 210-19(a) and 215-2(b) of NEC).

4 The grounding conductor shall be colored or identified as specified in the NEC. Grounding conductor size for

copper wire is not required to be larger than input conductor (Article 250-95 of NEC).

OM-206 Page 7

Have only qualified persons make

this installation.

Remove wrapper.

1 Line Disconnect Device Of

Proper Rating

2 Input Conductors

3 Grounding Conductor

Select size and length using

Table 3-2. Conductor rating must

comply with national, state, and lo-

cal electrical codes.

Strip 3/8 in (10 mm) insulation off

all conductors.

4 Strain Relief Connector

Insert conductors through strain

relief.

5 Input Terminal Block

6 Line Terminals

7 Ground Terminal

Insert grounding conductor into

grounding terminal and tighten

screw.

Insert each input conductor into

proper screw terminal L1, L2, or L3

on terminal block and tighten

screws.

Install and connect grounding

conductor and input conductors in

conduit or equivalent to deener-

gized line disconnect device.

Be sure grounding conductor goes

to an earth ground.

Reinstall wrapper.

8 Overcurrent Protection

Select type and size using

Table 3-2. Install into deenergized

line disconnect device (fused

disconnect switch shown)

ssb2.4* 3/93 – ST-145 667-B / SA-145 666-B

Tools Needed:

5/16 in

Figure 3-8. Input Power Connections

OM-206 Page 8

SECTION 4 – OPERATION

WARNING

ELECTRIC SHOCK can kill.

• Always wear dry insulating gloves.

• Insulate yourself from work and ground.

• Do not touch live electrical parts.

• Keep all panels and covers securely in place.

FUMES AND GASES can be hazardous

to your health.

• Keep your head out of the fumes.

• Ventilate area, or use breathing device.

• Read Material Safety Data Sheets (MSDSs) and

manufacturer’s instructions for material used.

WELDING can cause fire or explosion.

• Do not weld near flammable material.

• Watch for fire; keep extinguisher nearby.

• Do not locate unit over combustible surfaces.

• Do not weld on closed containers.

• Allow work and equipment to cool before handling.

ARC RAYS can burn eyes and skin;

NOISE can damage hearing.

• Wear welding helmet with correct shade of filter.

• Wear correct eye, ear, and body protection.

MOVING PARTS can cause injury.

• Keep away from moving parts.

• Keep all doors, panels, covers, and guards closed

and securely in place.

MAGNETIC FIELDS FROM HIGH CUR-

RENTS can affect pacemaker operation.

• Pacemaker wearers keep away.

• Wearers should consult their doctor before going

near arc welding, gouging, or spot welding opera-

tions.

See Safety Precautions at beginning of manual for ba-

sic welding safety information.

swarn6.1 10/91

ST-152 127

1 Amperage Adjustment

Control

2 Amperage Control Switch

3 Output (Contactor) Switch

4 Touch Start Switch

5 Weld Process Switch

6 Power Switch

7 Pilot Light

8 Optional Amperage/Voltage

Meter And Switch

34 5 6

Figure 4-1. Controls

1 Insulating Gloves

2 Safety Glasses With Side

Shields

3 Welding Helmet

Wear dry insulating gloves, safety

glasses with side shields, and a

welding helmet with a correct

shade of filter (see ANSI Z49.1).

2 3

sb3.1 10/91

Figure 4-2. Safety Equipment

1 Work Clamp

Connect work clamp to a clean,

paint-free location on workpiece,

as close to weld area as possible.

Use wire brush or sandpaper to

clean metal at weld joint area. Use

chipping hammer to remove slag

after welding.

sb4.1 2/93

Tools Needed:

Figure 4-3. Work Clamp

OM-206 Page 9

WARNING

ELECTRIC SHOCK can kill.

• Do not touch live electrical parts.

• Do not touch weld output receptacles when contactor is energized.

• Do not touch electrode and work clamp at the same time.

swarn7.1* 10/91

1 Output (Contactor) Switch

Use switch to select way of control-

ling output.

For front panel control, place

switch in On position.

For remote control, place switch in

Remote 14 position (see Section

3-5).

Weld output receptacles are energized

when switch is On and Power is On.

Figure 4-4. Output (Contactor) Switch

ST-159 059 / Ref. SC-140 372-C / S-0769

1 Amperage Adjustment Control

Use control to select weld amper-

age. Amperage may be adjusted

while welding.

2 Amperage Control Switch

Use switch to select way of control-

ling amperage adjustment.

For front panel control, place switch

in the Panel position.

For remote control, place switch in

Remote 14 position (see Section

3-5).

3 Remote Foot Control

4 Remote Hand Dial

5 Remote Fingertip Control

See Example below.

Set Switches Adjust Remote ControlSet Control

EXAMPLE Of Combination Remote Amperage Control

Control

Setting

(80 A)

Unit

Minimum

Figure 4-5. Amperage Controls

OM-206 Page 10

1 Weld Process Switch

Use switch to select type of weld

output current. Use GTAW position

for Gas Tungsten Arc Welding.

Use SMAW position for Shielded

Metal Arc Welding.

Switch position determines the op-

eration of the Touch Start switch

(see Figure 4-7).

Figure 4-6. Weld Process Switch

Touch Start switch must be in Off position when using a High-Frequency unit with

this welding power source, or when using the SMAW welding process.

NOTE

1 Touch Start Switch

Use switch to select touch start On

or Off.

With touch start On, start an arc in

GTAW welding as follows:

2 GTAW Electrode

3 Workpiece

Touch tungsten electrode to work-

piece at weld start point, hold elec-

trode to workpiece for 1-2 sec-

onds, and slowly lift electrode. An

arc will form when electrode is

lifted.

Normal open-circuit voltage is not

present before tungsten electrode

touches workpiece; only a low

sensing voltage is present be-

tween electrode and workpiece.

The solid-state output contactor

does not energize until after tung-

sten electrode is touching work-

piece. This allows electrode to

touch workpiece without overheat-

ing, sticking, or getting contami-

nated.

1 – 2

Seconds

“Touch”

Do NOT Strike Like A Match!

Ref. S-156 279

Figure 4-7. Touch Start Switch

1 Power Switch

Use switch to turn unit and pilot

light On and Off.

2 Pilot Light

Figure 4-8. Power Switch And Pilot Light

OM-206 Page 11

1 Amperage/Voltage Meter

Meter displays amperage or volt-

age output.

2 Meter Switch

Use switch to select amperage (A)

or voltage (V) display.

In Volts position, the meter dis-

plays the voltage at the weld output

receptacles. In Amperage posi-

tion, the meter displays the welding

current during welding, and the

preset amperage when welding is

not taking place.

The meter displays the actual val-

ue for 15 seconds after welding

stops (see Section 5-4).

Figure 4-9. Optional Amperage/Voltage Meter And Switch

Turn On

Shielding Gas

ssb8.1 12/92

Install &

Connect

Equipment

Install & Connect

High-Frequency

Unit

Select

Tungsten (See

Section 7)

Insert

Tungsten

Into Torch

Put On

Personal Safety

Equipment

Set Controls

Turn On

High-Frequency

Unit

Turn On

Welding Power

Source

Begin Welding

Figure 4-10. Sequence Of Gas Tungsten Arc Welding (GTAW)

Install &

Connect

Equipment

Install & Connect

Pulser Control

Unit

Install & Connect

High-Frequency

Unit

Insert

Tungsten

Into Torch

Put On

Personal Safety

Equipment

Set Controls

Turn On

Shielding Gas

Turn On

Welding Power

Source

Begin Welding

Turn On Pulser

And High-

Frequency Unit

Select

Tungsten (See

Section 7)

Figure 4-11. Sequence Of Gas Tungsten Arc Welding - Pulsed (GTAW-P)

Begin Welding

ssb7.1 9/92

Install &

Connect

Equipment

Select

Electrode

Put On

Personal Safety

Equipment

Set Controls

Insert

Electrode

Into Holder

Turn On

Welding Power

Source

Figure 4-12. Sequence Of Shielded Metal Arc Welding (SMAW)

OM-206 Page 12

SECTION 5 – MAINTENANCE & TROUBLESHOOTING

WARNING

ELECTRIC SHOCK can kill;

SIGNIFICANT DC VOLTAGE exists after

removal of input power.

• Do not touch live electrical parts.

• Turn Off welding power source, disconnect input

power, wait 60 seconds, measure voltage on input

capacitors according to Section 5-3, and wait for

voltage to drop to zero before touching any parts.

HOT PARTS can cause severe burns.

• Allow cooling period before maintaining or

servicing.

MOVING PARTS can cause injury.

• Keep away from moving parts.

STATIC ELECTRICITY can damage parts

on circuit boards.

• Put on grounded wrist strap BEFORE handling

boards or parts.

Maintenance to be performed only by qualified

persons.

swarn8.1* 2/93

5-1. Routine Maintenance

Turn Off all power before maintaining.

3 Months

Blow Out

Vacuum

Inside

Replace

Unreadable

Labels

6 Months

Tape Or

Replace

Cracked

Cables

ST-145 666-B

Clean

And

Tighten

Weld

Connections

3 Months

14-Pin Cord

Gas

Hose

Torch Cable

Replace

Cracked

Parts

See

Section

3-3

– –

3-4

– –

Figure 5-1. Maintenance Schedule

5-2. Overload Protection

Thermostats TP1 and TP2 protect the unit from damage due to overheating. If the unit gets too hot, TP1 and/or TP2

open and weld output stops. The pilot light stays on, and the fan keeps running to cool the transformer. Wait several

minutes before trying to weld.

OM-206 Page 13

5-3. Measuring Input Capacitor Voltage

READ SAFETY BLOCKS at start of

Section 5 before proceeding.

WARNING

ST-153 136-A

Turn Off welding power source and

disconnect input power.

Remove wrapper.

1 Input Capacitor C1 (Both

Models)

2 Input Capacitor C2 (175

Models Only)

3 Voltmeter

Check input capacitor(s).

Measure the dc voltage across the

positive (+) and negative (–) termi-

nals every 30 seconds until voltage

drops to 0 (zero) volts.

Proceed with job inside unit.

Reinstall wrapper when finished.

Tools Needed:

5/16 in

Significant DC voltage can remain on capacitors after unit

is Off. Always check capacitors as shown to be sure they

have discharged before working on unit.

Figure 5-2. Measuring Input Capacitor Voltage

5-4. Changing Amperage/Voltage Meter Hold Function

READ SAFETY BLOCKS at start of

Section 5 before proceeding.

WARNING

The Amperage/Voltage meter is

able to hold the displayed weld out-

put value for 15 seconds after

welding stops. This procedure al-

lows the hold function to be turned

On or Off.

If the hold function is not used, the

displayed value leaves when weld-

ing stops.

Turn Off welding power source,

disconnect input power, and check

voltage on input capacitors ac-

cording to Section 5-3 before pro-

ceeding.

1 A/V Meter Board PC3

2 DIP Switch S2

3 Toggle 1

4 Toggle 2

Set toggles in desired position. Re-

install wrapper.

ST-158 741

Tools Needed:

Hold Used

Hold Not Used

OFF

Figure 5-3. Changing Amperage/Voltage Meter Hold Function

OM-206 Page 14

5-5. Troubleshooting

ELECTRIC SHOCK can kill.

SIGNIFICANT DC VOLTAGE exists after

removal of input power.

• Do not touch live electrical parts.

• Turn Off welding power source, disconnect input

power, wait 60 seconds, measure voltage on input

capacitors according to Section 5-3, and wait for

voltage to drop to zero before touching any parts.

HOT PARTS can cause severe burns.

• Allow cooling period before servicing.

MOVING PARTS can cause injury.

• Keep away from moving parts.

STATIC ELECTRICITY can damage parts

on circuit boards.

• Put on grounded wrist strap BEFORE handling

boards or parts.

• Use proper static-proof bags and boxes.

Troubleshooting to be performed only by qualified

persons.

WARNING

swarn9.1* 2/93

Table 5-1. Welding Trouble

Trouble Remedy Section

No weld output; unit completely inop-

erative.

Be sure Power switch is On. Figure 4-8

Secure power cord plug in receptacle (152 model). 3-6A

Be sure line disconnect switch is On (175 model). 3-6B

Check line fuse(s) and replace if necessary. Reset circuit

breakers.

3-6

Check for proper input power connections. 3-6

No weld output; fan motor running and

pilot light on.

Check position of Output (Contactor) switch. Figure 4-4

Thermostats TP1 and/or TP2 open (overheating). Allow fan to

run; thermostat(s) closes when unit has cooled.

5-2

Low weld output with no control. Check position of Amperage Control switch. Figure 4-5

Have Factory Authorized Service Station/Service Distributor

check control board PC1.

– –

Limited output and low open-circuit

voltage.

Check incoming power for correct voltage. Replace line fuse if

open or reset circuit breaker.

3-6

Check for proper input and output connections. 3-3, 3-4, 3-6

Erratic or improper weld output. Tighten all welding cable connections. 3-3, 3-4

Check for proper size and type of cable. 3-3

Check for proper input and output connections. 3-3, 3-4, 3-6

Replace electrode. 7-1, 7-2

Arc not forming when using Touch

Start.

Check electrode and workpiece, clean as needed to allow good

contact.

– –

Fan motor does not run. Check and clear blocked fan blade; be sure blade is secure on

shaft.

– –

Have Factory Authorized Service Station/Service Distributor

check fan motor.

– –

OM-206 Page 15

Trouble Remedy Section

Wandering arc; poor control of arc di-

rection.

Reduce gas flow rate. – –

Select proper size tungsten. 7-1

Properly prepare tungsten. 7-2

Tungsten electrode oxidizing and not

remaining bright after conclusion of

weld.

Shield weld zone from drafts. – –

Increase postflow time. – –

Check and tighten all gas fittings. – –

Water in torch. Refer to torch Owner’s Manual for part(s) requir-

ing replacement, and repair torch as necessary.

– –

OM-206 Page 16

SECTION 6 – ELECTRICAL DIAGRAMS

Figure 6-1. Circuit Diagram For 152 Model

SC-158 547-A

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Miller MT-24 F-25-1 Owner's manual

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Model: MT-24 F-25-1

Category: Welding System

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